#include <functional>
#include <iostream>
int main() {
  int foo = 4;
  int foo1 = foo; // 4
  std::cout << "foo address:" << &foo << " value = " << foo
            << " foo1 address : " << &foo1 << " foo1 value : " << foo1 << "\n";
  auto bar = std::ref(foo); // 4
  bar++;                    // 5
  std::cout << "origin address : " << &foo << " origin value " << foo
            << " foo1 address : " << &foo1 << " foo1 value: " << foo1
            << " bar address : " << &bar << " ref value:" << bar;
}
